Sony DWTB01/E3040 Product Information Document (Digirtal Wireless System Integ - Page 52

Configuring a DWX System Step 4 Checking Third-order Intermodulation Distortion Procedure Power up all transmitters for channels other than the desired channel, and generate third-order intermodulation distortion (subsequently called interference) in the receiver for the desired channel. Assign a range of parameters for TX output power and RX attenuator settings and check the interference noise level with each setting. 14 Power up all transmitters for channels other than the desired channel. Establish a setup simulating the expected conditions during actual operation, and have a person with the TX stand in a position closest to the antenna. Example: If the TX is the DWM-01, it should be held in the hand, close to the mouth. If the TX is the DWT-B01, it should be worn on the hip, and the person should stand at the rim of the stage, approaching the antenna. * Equipment other than TX (RX, boosters, etc.) should be constantly on. 15 Using the RF level meter of the RX set to the channel whose TX is switched off, check the thirdorder intermodulation distortion noise level in the channel. Setting example for checking  Band to use: Band established in step 1.  Group to use: Group established in step 1.  Antenna installation location/orientation: As determined in step 2.  Antenna gain: As determined in step 2.  Number of antennas: As determined in step 2.  TX RF power: Setting that cleared the requirements of step 3.  RX attenuator: Setting that cleared the requirements of step 3. Check procedure Check the RF level meter indication.  In principle, the noise level should be less than 10 dBμ (RF level meter should be consistently out). Sample results 10 dB RX ATT 5 dB TX RF power 1 mW 10 mW Step 3 Step 4 Step 3 Step 4 Setting 1 Setting 4 Poor (Good) Good Good Setting 2 Setting 5 Fair (Good) Good Good Note 0 dB Setting 3 Good Good Setting 6 Good Fair For stable reception, sufficient RF power levels should be obtained in the desired channel, and at the same time, the D/U ratio between desired channel and interference should be at least 20 dB. Decreasing the system-wide RF level will decrease interference in the desired channel by a factor of 3. Consequently, if the D/U ratio is insufficient, reducing the RF lower will provide an improvement. For example, when a 5 dB attenuation is introduced, the level in the desired channel will decrease by 5 dB, but the interference level will decrease by 15 dB, thereby yielding an improvement in D/U ratio by 10 dB. The same applies to the attenuation of RF power due to distance. If the RF level is too low, the available distance will decrease, resulting in an insufficient service area. But if the RF level is very high, this also can cause problems because the required D/U ratio cannot be obtained in the antenna vicinity. The resulting service area will be shaped like a doughnut, with a large hole in the middle, which also is undesirable. Therefore, 50 mW output of the TX is not suited for simultaneous multi-channel operation. TX RF power Low High RX ATT High A B Low C Small Service area for single channel Low Third-order intermodulation distortion noise level High Large Zone A Interference is low, but RF level in desired channel is also low, resulting in insufficient service area. Zone B Good balance between desired channel and interference RF level. Desired service area is achieved, also during simultaneous multi-channel operation. Zone C RF level in desired channel is high, but interference level is also high. During simultaneous multi-channel operation, desired service area will not be achieved in antenna vicinity. Service area 52 Making and Checking RF Settings (UHF)